How to delete specific edge using python?
Fill the circle primitive.
Going by the demonstration it appears you wish to have a flat filled semi circle.
In which case recommend filling the circle when created, then ditching the extrude and fill operators.
Test script, have chosen a triangular fan fill for the circle, for an ngon, choose 'NGON'

import bpy


# Draw hemisphere of 1m radius
bpy.ops.mesh.primitive_circle_add(
    radius=1, 
    enter_editmode=True, 
    align='WORLD', 
    location=(0, 0, 0), 
    fill_type='TRIFAN',  # NOTHING  or NGON
    )
    
bpy.ops.mesh.bisect(
    plane_co=(0, 0, 0), 
    plane_no=(0, -1, 0), 
    clear_inner=True,
    )

In question code after the bisect operator the verts on bisect line are selected. The extrude move operator creates an edge for each from original vert to 2 units in x direction.